SGER: Extent and Impact of Distal Ash Fallout From the May 2008 Eruption of Chaiten, Chile

这项探索性研究的小额赠款将支持南佛罗里达大学（USF）的一个科学家团队与阿根廷的一个国际火山学家小组合作，该小组目前正在研究智利Chaitén火山持续喷发的新火山沉积物。 柴腾火山于2008年5月2日开始喷发，显然是在大约9,500年的平静之后。这次持续的火山爆发已经是自1991年哈德逊火山爆发以来南美洲最大的一次，并创造了一个独特的机会，可以详细地对火山灰沉降物进行采样，特别是因为火山灰沉降物主要分布在阿根廷东部。来自USF的团队与他们的国际合作者一起，计划在2008年6月和7月初对阿根廷南部的火山灰沉降物进行采样，这是存款最远和最容易被侵蚀的部分。这次考察的主要目的是测量一个广泛分布的火山灰落存款的厚度、粒度和质量负荷的变化。这些数据将有助于确定喷发物质的体积，并将对目前火山灰散布和沉积的模型进行检验。此外，他们还将与同事合作，确定与新鲜掉落的火山灰有关的易溶盐的物理和化学特性。这些数据为确定火山灰沉降物的潜在地球化学影响提供了必要的信息。还计划使用主动泵送过滤器测量细空气灰（包括新落下的和重新悬浮的）的粒度特征，这是火山灰落下对健康的潜在影响模型的一项重要投入。 最终，他们计划使用过去十年开发的TEPHRA 2数值模型来模拟柴腾火山爆发的火山灰沉降物。虽然这个和其他沉降物模型已被广泛用于预测火山危险，但尚未有机会验证这些模型用于直接观察和在火山碎屑沉积后不久取样的大型爆炸性火山爆发。因此，柴腾火山爆发提供了一个难得的机会，收集数据，以验证和改进TEPHRA 2数值模型。例如，预测距离火山喷发数百公里处的极细火山灰沉积的能力尚未得到充分测试，但这对健康和经济产生了重大影响。利用现场收集的数据，该小组将使用TEPHRA 2，再加上非线性反演技术，估计喷发参数（柱高，持续时间，质量流量），并与喷发的观测结果进行比较。所有结果都将通过IAVCEI Tephra工作组网站提供给火山学界。

This Small Grant for Exploratory research will support the travel of a team of scientists from the University of South Florida (USF) to collaborate with an international group of volcanologists in Argentina that are currently studying the new volcanic deposits from the ongoing eruption of Chaitén volcano in Chile. Chaitén volcano began erupting on May 2, 2008, apparently after approximately 9,500 years of quiescence. This ongoing eruption is already the largest in South America since the 1991 eruption of Hudson volcano, and creates a unique opportunity to sample tephra fallout from the eruption in detail, particularly because the tephra fallout is distributed primarily eastward, across Argentina. The team from USF, together with their international collaborators, plan a rapid response to this event by sampling tephra fallout across southern Argentina, the most distal and easily eroded parts of the deposit, in June and early July, 2008. The primary goal of this excursion will be to measure the variation of thickness, grain-size, and mass loading across a widespread tephra fall deposit. Such data will allow the determination of the volume of erupted material; and will provide a test of the current models of tephra dispersal and deposition. In addition, they will work with colleagues to determine the physical and chemical characteristics of the readily-soluble salts associated with freshly-fallen tephra. Such data provide essential information for determining the potential geochemical impact of ash fallout. It is also planned to measure the grain-size characteristics of fine airborne-ash (both freshly falling, and re-suspended), using actively-pumped filters, an essential input for models of the potential health impacts of volcanic ashfall. Ultimately, they plan to use the TEPHRA2 numerical model developed over the past decade to model tephra fallout from the Chaitén eruption. Although this and other fallout models have been widely used to forecast volcano hazards there has not yet been an opportunity to validate these models for large explosive volcanic eruptions that have been directly observed and sampled soon after tephra deposition. Thus, the Chaitén eruption provides a rare opportunity to collect data to validate and improve the TEPHRA 2 numerical model. For example, the ability to forecast deposition of very fine ash hundreds of kilometers from the erupting volcano has not yet been adequately tested yet represents a major health and economic impact. With the data collected in the field, the team will use TEPHRA2, coupled with nonlinear inversion techniques, to estimate eruption parameters (column height, duration, mass flow), and compare with observations of the eruption. All results will be available to the volcanology community via the IAVCEI Tephra Working Group website.